Two Cases of Well Controlled Chronic Spontaneous Urticaria Triggered by the Moderna COVID-19 Vaccine.

Chronic spontaneous urticaria (CSU, chronic idiopathic urticaria) is a clinical diagnosis characterized by recurrent urticaria of unknown origin, with or without angioedema, that occurs for six weeks or longer. Management of CSU includes a second-generation H1 antihistamine and/or elimination of exacerbating factors. If initial treatment is unsuccessful, trials of first generation H1 antihistamine, H2 blocking antihistamine, leukotriene-receptor antagonist, anti-inflammatory or immunosuppressive agents may be administered. Exacerbating factors include stress, environmental conditions, medications, physical stimuli, and infections. We report the first two cases of a COVID-19 vaccine triggered relapse of CSU that was previously well controlled on therapy.